Tobacco smoke filter containing a sugar ester



Nov. 14, 1961 G. P. TOUEY EI'AL 3,008,474

TOBACCO SMOKE FILTER CONTAINING A SUGAR ESTER Filed April 13, 1959 F19.

A POWDERED ADDITIVE BONDED TO CELLULOSE ACETATE FILAMENTS BY MEANS OF ALIQUID. SUGAR ESTER souo ; PARTICLE 3 5 SUGAR U. ADHESIVE E FILAMENT AIRFLOW I Fig. 4 A CRYSTALLINE SUGAR ESTER ADHERING TO CELLULOSE ACETATEFILAMENTS AIR FLOW GEORGE I? TOUE) ROBERT C. MUMPOWER INVEN T 0R5ATTORNEYS AIR F LOW United States Patent 3,008,474 TOBACCO SMOKE FILTERCONTAINING A SUGAR ESTER George P. Touey and Robert C. Mumpower II,Kingsport, Tenn., assignors to Eastman Kodak Company,

Rochester, N.Y., a corporation of New Jersey Filed Apr. 13, 1959, Ser.No. 805,729 5 Claims. (Cl. 131-208) This invention relates to improvedtobacco smoke filters. More particularly, this invention concerns afilter which contains certain sugar esters in its make/up.

Tobacco smoke filters prepared from crimped, continuous, man-madefilaments have found considerable use in the industry. It has beenproposed to improve such filament filters by applying additives to thesurface of the filaments making up such filters. Although theincorporation of additives onto the surface of the filaments improvesthe filters made from such filaments, certain problems have arisen. Thatis, certain of the prior procedures for applying additives do notsufficiently bond the additive to the filaments with the result that theadditive may sift out and its effect of improving filtration efficiencythereby becomes lost. Also, if the additive tends to sift out andthereby may get into the smokers mouth, this may be objectionable.

In other words, since tobacco smoke filters are usually held in thesmokers mouth, or if a holder is employed, even then the filter is nearthe smokers mouth, it is apparent that many materials althoughfunctioning as strong adhesives, because of taste, odor and for otherreasons, are not suitable for bonding agents for such type of filtermanufacture. Also, certain materials that have adhesive propertiesexhibit such adhesiveness at the onset thereby presenting problems ofgumming the filter making equipment and plugging spray equipment.

Therefore, it is thought apparent that the development of a materialwhich functions in an improved manner as a bonding agent, an additiveand the like in the manufacture of tobacco smoke filters represents ahighly desirable result. After extended investigation, we have foundcertain sugar esters which are readily compatible with the variousmaterials employed in tobacco smoke filter manufacture and we believethat our use of such esters in the manufacture of tobacco smoke filtersis new, unobvious and advantageous.

This invention has for one object to provide a better method for bondingpowdered additives to the filaments of a cellulose acetate tow type ofcigarette filter. Another object is to provide a way of producing apermanent bond between the additive and the filaments without resortingto the use of adhesives dissolved in volatile solvents or dissolved inwater. Another object is to provide a non-tacky bonding agent for use inproducing cellulose acetate filters containing powdered additives. Stillanother object is to provide a method of producing protrusions on thesurfaces of filaments of cigarette filter material without having todust or spray on a powdered additive. A still further object is toprovide an additive for a textile type filter material which can beapplied to the filaments as a liquid and after being spread on thefilaments as a liquid it will gradually crystallize forming bumps orprotrusions on the surfaces of the longitudinally aligned filamentsafter the filter is prepared. A further object is to disclose a textiletow type of ciga' rette filter containing finely divided solid particleson its filament surfaces, said particles showing no tendency to3,008,474 Patented Nov. 14, 1961 sift out of the filter when it istapped. Other objects will appear hereinafter.

In the broader aspects of the present invention, we have found thatcertain materials which, for convenience of reference, we willgenerically refer to as sugar esters, may be used in various ways in themanufacture of tobacco smoke filters. These sugar ester materials whichwill be described in more detail hereinafter, not only function tostrongly bond additives, but are compatible with existing materials usedin filter manufacture and are not objectionable from the standpoint oftaste and odor and are otherwise advantageous.

For assistance in a better understanding of this invention, referencemay be made to the attached drawing forming a part of the instantapplication.

FIG. 1 is a schematic view on an enlarged scale of a bundle of filamentscarrying a powdered additive in accordance with one embodiment of thepresent invention;

FIG. 2 likewise is a view on an enlarged scale of a single filament forbetter illustrating the bonding of the additive;

FIG. 3 is a detail view of a section of a single filament for furthershowing in a magnified magnner the bonding of the additive;

FIG. 4 is a view similar to FIG. 1 but of another embodiment inaccordance with the present invention wherein the sugar ester comprisesthe additive; and

FIG. 5 is a view on an exaggerated scale of a single filament forfurther illustrating the embodiment of FIG. 4

Referring to FIG. 1, a continuous crimped cellulose acetate filament isshown at 2. Such filaments would carry a powdered additive 3 on thesurface of the filament and bonded thereto. The bonding of the additiveto the filament is better shown in FIGS. 2 and 3 where the sugar esterbonding agent of the present invention is indicated at 4 and 5.

FIG. 4 illustrates an embodiment described later on in the instantspecification wherein the sugar ester itself crystallizes out on thesurface of the filament thereby comprising the additive. That is, inFIG. 4 the cellulose acetate filament is shown at 6 and the surface ofsuch type filaments carries the sugar ester additive as illustrated at7. This is shown on a somewhat larger scale in FIG. 5 where the carrierfilament is designated 8 and the sugar ester additive which crystallizesout is designated 9.

One method of operation is accomplished by spraying a spread outcellulose acetate filter tow with a solution consisting of 10-80%plasticizer and -20% of a sugar ester of the present invention prior tothe application of a powdered additive. The plasticizer is chosen fromone of the organic plasticizers already mentioned in prior patents asbeing capable of producing a rigid cellulose acetate tow filter. Thesugar ester to be dissolved in the plasticizer preferably is anoncrystallizing highly viscous organic solvent soluble derivativecapable of producing a viscous tacky liquid film. Mixed aliphatic acidesters of glucose and sucrose of the present invention are typicalnoncrystallizing sugar esters. The following are further examples ofsuch esters:

Glucose acetate propionate Glucose acetate isobutyrate Glucosepropionate isobutyrate Sucrose acetate propionate Sucrose acetateisobutyrate Sucrose propionate isobutyra-te These mixed esters areunlike the unmixed completely esterified acetates, propionates andisobutyrates of glucose and sucrose which are well defined crystallinecompounds. These esters are unique in their ability to remain as highlyviscous liquids for an indefinite period of time at ordinarytemperatures. Such noncrystallizing highly viscous esters of sucrose andglucose are described in the Touey and Davis U. S. Patent No. 2,931,802.They are extremely viscous liquids at room temperature but formnon-tacky, nonvolatile and sprayable solutions when dissolved in theplasticizers used as bonding agents for cellulose acetate tow filters.This non-tacky property of such solutions can be obtained even thoughthe sugar ester content of the combination is as high as 80%.

Thus, with this new method for firmly bonding powders to the filamentsurfaces in a cellulose acetate tow filter, one does not need toevaporate off water or an organic solvent. The plasticizer-sugar estersolution is simply sprayed on the tow prior to the additive dustingoperation. Then the tow is treated with the additive and compacted intoa paper-wrapped filter in the usual manner. As the filter is stored,most of the plasticizer dissolves into the filaments in the usualmanner. However, most of the sugar ester component of the sprayingliquid remains on the surface of the filaments and becomes quite tackydue to the extraction of the plasticizer by the cellulose acetatefilament. Thus, a tacky adhesive surface is formed on the filamentsafter the filter has been fabricated. This tacky surface in turnprevents the additive from sifting out of the filter after most of theplasticizer has been absorbed by the filaments.

A valuable distinction between the pl asticizer-sugar ester technique ofthe present invention and the adhesive in a volatile solvent techniquefor producing a tacky surface for acceptance of the additive lies in thefact that the new method does not produce a tacky surface during thefabrication of the filter. The tacky surface gradually forms after thefilter has been prepared and as the plasticizer gradually is absorbedinto the cellulose acetate filaments. Therefore, no problems of filterfabrication due to a tacky tow are encountered. Another distinction isthat there is no volatile solvent (including water) to be evaporatedduring the processing of the filter rod. These distinctions are quiteimportant when cellulose acetate tow cigarette filters are prepared inthe rapid economical manner described by the Crawford and StevensPatents 2,794,239 and 2,794,480.

The amount of sugar ester which is added to the tow filaments to achieveadequate bonding of the additive to its surface will depend upon thetype and amount of additive employed. Thus, with light powders such ascellulose, starch and the like, an amount between 3 and 10% based on theentire filter combination (without the paper) is sufficient. With theheavier additives such as calcium carbonate, the sugar esterconcentration preferably is in the range of 8 and 15%. The particularnoncrystallizing sugar ester of this invention does not seem to becritical. All are extremely tacky, highly viscous, nonodorous liquids attemperatures below 50 C.

The amount of plasticizer which may be used will depend on two factors:the degree of filter hardness desired and the ability of the plasticizerto reduce the viscosity and tackiness of the spraying solution. In anycase, the minimum plasticizer content of the unwrapped filter usuallywill not be below 5% or above 25%. The preferred range of plasticizercontent in the unwrapped filter is between 7 and 18%.

The following examples will further illustrate this species of theinvention. In these examples reference is made to standard cigarettes.These were domestic, unfiltered, king-size (85 mm.) cigarettes chosenfrom two cartons (400) of the same brand of cigarettes. Their selectionwas made on the basis of the average weight of the 400 cigarettes. Onlythose weighing Within 2% of the average weight of the 400 cigaretteswere used in the smoking tests.

4 EXAMPLE l-A A crimped (12 crimps/in.), continuous, tow of celluloseacetate filaments containing 12,000 filaments of 5 denier per filamentwas pulled across a compressed air device which bloomed it out to awidth of 12 inches. Immediately after this treatment, the spread out towwas pulled through a spraying chamber whereit was sprayed on both sideswith a solution consisting of 50 parts glycerol triacetate and 50 partsof sucrose acetate isobutyrat'e'. The filaments were then led through adusting chamber whereupon they were dusted on both sides with a finelydivided activated carbon powder. From the dusting chainber the tow waspulled through a device which compacted it and paper wrapped it into theform of a continuous rod 25.5 mm. in circumference. Finally, this rodwas cut into 15 mm. filter lengths.

The paper wrapper was removed from several of the filter tips foranalytical purposes. Analysis of these samples showed that the filtersconsisted of 46% cellulose acetate filaments, 11% of glyceroltriacetate, 11% sucrose acetate isobutyratc and 32% activated carbon.The sucrose ester used on this preparation contained 12.7% acetyl (CHC=O) and 47.4% isobutyryl (C H C=O).

The remainder of the filter rods were stored for a period of one week atroom temperature. After the first 24 hours the rods were considered tobe semifirm; however, after 48 hours they were firm due to the action ofthe glycerol triacetate on the cellulose acetate filaments. After astorage time of one week, it was not possible to dislodge the carbonparticles from the ends of the filters by tapping them vigorouslyagainst a smooth hard surface. Normally the activated carbon particlesmight have sifted out of the filters within 24 hours after theirpreparation if certain other materials had been used as the bondingagent.

Ten of the 15 mm. filters were attached to the standard cigarettes whichhad been shortened by 15 mm. These cigarettes were smoked to 30 mm. buttlengths on an automatic smoking machine which pulled a 35 ml. pufl? of 2seconds duration at the rate of one puff per minute. The main streamsmoke from the ten cigarettes was analyzed for volatile aldehydes by themethod described by G. P. Touey in Analytical Chemistry, vol. 27, page27 (1955). Another set of ten filtered cigarettes was prepared andsmoked in the manner described and in this case, the main stream smokewas analyzed for tar and nicotine content. The results of both of thesetests are shown in Table I.

EXAMPLE 1-B A crimped (l2 crimps/ in.) continuous tow of celluloseacetate filaments containing 16,000 filaments of 5 denier per filamentwas bloomed out to a width of 12 inches. The spread out tow was thensprayed on both sides with glycerol triacetate. After the sprayingoperation, it was processed into 15 mm. filters in the manner describedabove.

Within 24 hours, the filters were quite firm. Ten of these filters wereattached to the standard cigarettes which had been shortened by 15 mm.and the cigarettes were automatically smoked to 30 mm. butt lengths. Themain stream smoke from the ten cigarettes was analyzed for volatilealdehydes. Another set of ten filtered cigarettes was prepared andsmoked in the manner described and in this case, the main stream smokewas analyzed for tar and nicotine content. The results of both of thesetests are shown in Table I.

EXAMPLE 1-C Ten of the unshortened standard cigarettes containing nofilters were smoked to 30 mm. butt lengths and the main stream smoke wasanalyzed for volatile aldehydes. Another 10 of the unshortened standardcigarettes were smoked in a similar manner and the main stream smoke wasanalyzed for tar and nicotine. The results of these tests are shown inTable I.

Table I Mg. Alde- Average Volatile Mg. Tar Mg. hydes Tar NicotineCigarettes Cigarette Alde- From 10 Nicotine Removed Removed RemovedPressure hydes Cigarettes From 10 by Filter, by Filter, by Fllter, DropFrom 10 Cigarettes percent percent percent Cigarettes Example l-C (nofilter) 3.1 10. 9 170 26 Example 1-B (filter without activated carbon)3. 8 10. 3 140 21. 5 18 17 Example l-A (filter containing activatedcarbon) 4.1 7.9 119 19.0 26 30 27 EXAMPLE 2 sistiug of 63% sucrosepropionate isobutyrate and 37% len co onoacetate. This solution was thenThlS example lllustrates the inability of plastrcizer alone 15 2 d g glace of the Solution of Example 3 to bond the activated carbon to thetow in a manner as p y p firmly as the bonding of the present invention.P t

GI'CGH A cr1mped (12 cr1mps/1n cont1nuous tow of cellu- Percent Percentsums, Type of Percent lose acetate filaments containing 12,000 filamentsof 5 20 Filter Fila- Plas- Pi0p10- Kggdered {gauged denier per filamentwas bloomed out and sprayed on both 35 1 we We sides with glyceroltriacetate. Then it was dusted imty atc mediately and on both sides withthe same brand of activated carbon powder as used for Example 1. Thedusted 66.1 5. 9 10 Starch 1s 53.1 8.9 CaCO 23 tow was then convertedInto filters 1n the manner de- 657 9 scribed in Example 1. The filtersconsisted of 51% cellulose acetate fibers, 23% glycerol triacetateplasticizer and 26% carbon powder, based on the total combinationwithout the paper wrapper. Thus, in this case, the amount of plasticizerin the filters was slightly higher than the total amount of plasticizerand sugar ester in the filters of Example 1.

When first prepared, only a slight trace of carbon could be dislodgedfrom the filters by tapping them against a hard surface. However, aftera period of time a significant amount of the carbon powder could bedislodged from the filter in this manner. This condition grew morepronounced as the age of the filters increased.

EXAMPLE 3 This example illustrates the ability of sucrose acetatepropionate to strongly bond powders of starch, calcium carbonate andground cellulose to cellulose acetate tow filaments in the form of acigarette filter.

A 30-ft. section of a crimped (12 crimps/ in.) cellulose acetate tow of12,000 filaments of 5 denier per filament was divided into 3 equallengths. All of the samples were then bloomed out to a width of 12inches and sprayed on both sides with a solution consisting of 75%sucrose acetate propionate and propylene glycol monoacetate. The firstsample was then dusted on both sides with rice starch. The second andthird samples were dusted on both sides with calcium carbonate andground cellulose respectively. All of the samples were then processedinto filters in the manner described in Example 1.

Percent Percent Percent Sucrose Type of Percent Filter Fila- Plas-Acetate Powdered Powdered ments ticizer Propio- Additive Additive nate60 7. 0 12 Starch 21 49. 7 9. 3 16 OaOO; 25 63.6 6. 4 11 Oellulose l9After a period of one months storage, there was no indication of looselybound powders in the filters when they were tapped on a hard surface.Subsequent smoking tests indicated that the filters were capable ofremoving 32-40% more tars from the smoke of the standard cigarette thanthe 15 mm. length of tobacco they replaced.

EXAMPLE 4 The work in Example 3 was repeated. However, in this example,a noncrystallizing sucrose propionate isobutyrate was dissolved in theplasticizer to produce a solution con- After a period of one monthsstorage, there was no evidence of loosely bound additive in any of thefilters when they were tapped on a hard surface. Subsequent smokingtests indicated that the filters of the present invention removedapproximately 6 more of the tars from the smoke of the standardcigarette than the 15 mm. length of tobacco they replaced.

In the above description and examples we have shown the use of our sugaresters somewhat in accordance with current tobacco smoke manufacturingprocedures. That is, we have shown that the sugar esters are compatiblewith plasticizers hence may be readily applied to improve themanufacture of additive filters wherein the filaments are sprayed with abonding agent and then the additive applied to the sprayed filaments. Inconnection with such use it will be observed that the sugar esters ofthe present invention are not tacky as initially used and, therefore, donot hamper manufacturing operations. However, our esters become tackyand strongly bond the additive as the filter may be stored for a period.

It has further been found that certain of our sugar esters may be usedto accomplish the function of the sugar esters themselves giving theadditive eifect by giving bumps and protrusions on the sprayedfilaments. This further improvement will be further apparent from thedescription which is now set forth.

This feature may be accomplished by spraying the continuous and crimpedtow material with a liquid consisting of a crystallizable sugar ester ofthe present invention dissolved in an organic solvent. At some point inthe continuous operation, the cord or tow is bloomed out to a width of612 inches to expose the separate filaments and while in this spread outcondition the solution of the sugar ester is applied to its top andbottom sides by means of conventional spray guns. Then the sprayed towis pulled back together and is pulled through that section of theapparatus which wraps it with a suitable paper and cuts it into filterrods having a circumference equal to that of a cigarette.

After the rods have been prepared, the particular sugar esters of thisinvention gradually crystallize on the filament surfaces of the filter,forming protrusions which exten-d into the spaces between thelongitudinally aligned filaments. These protrusions function as spotsfor impingement of part of the smoke particles which would channelthrough the filter.

The sugar esters for this species of our invention are chosen from thelow-molecular-weight aliphatic acid esters of glucose, sucrose, lactoseor from the low'molecular-Weight aliphatic acid esters of the simplesugar derivatives namely sorbitol, int-methyl glucoside and a-ethylglucoside.

GROUP I SUGAR ACETATES Glucose penta acetate Sucrose octaacetate Lactoseoctaacetate a=Metliyl D-glucoside tetraacetate' oz-Ethyl D-glucosidetetraacetate Sorbitol hexaacetate GROUP II SUGAR PROPIONATEIS ANDISOBUTYRATES Glucose penta propionate Glucose penta isobutyrate Sucroseoctapropionate Sucrose octaisobutyrate Lactose octaisobutyrate Lactoseoctapropionate All of these sugar esters are solid compounds at roomtemperature and all crystallize rather slowly from organic solvents evenwhen the concentration of the suger ester in the solvent is quite high.This unique property afiords the opportunity of applying them to the towas liquids which spread over the surfaces of the filaments before thecrystals begin to form. This leads to a better distribution of the solidadditive to the tow than can be obtained by dusting or spraying on apowdered additive. Also, since the solids form after the filter is made,there is no danger of the solids being displaced from the tow during itsconversion to a filter tip.

The amount and type of solvent which is used to prepare the sugar estersolution will now be described. Two types of solvents may be applied.The first type is the volatile solvent. These are usually aliphaticalcohols, esters and ketones. Examples of such solvents are methylalcohol, ethyl alcohol, isopropyl alcohol, methyl acetate, ethylacetate, acetone and the like. In the case of the volatile solvent theconcentration of the sugar ester can range from 30 to 90%. At the lowerconcentrations, i.e. 30-60% a good portion of the volatile solvent willevaporate during the spraying operation leaving a viscous solutioncontaining a residual amount of solvent. This residual amount of solventprevents the sugar from crystallizing. Then, as the filter rod is storedfor several hours or days, the residual solvent evaporates and the sugarderivative crystallizes on the filament surfaces.

The second type of solvent is the non-volatile solvent. This type isdesigned specifically for the cellulose acetate type of textile towfilter described in the Crawford and Stevens patents. It is selectedfrom those type of organic plasticizers which are solvents for the sugarester and which are also bonding or hardening agents for celluloseacetate tow filters. Examples of such solvents are glycerol diandtriacetate, alkylene glycol acetates, triethyl citrate, di[methoxyethyl] phthalate, ethyl phthalyl methyl glycollate, acetyl triethylcitrate, glyceral diand tripropionate and mixtures of such products withhigh boiling alcohols and glycols. When the non-volatile solvent is usedthe amount of solvent is more critical. Thus, the solvent concentrationpreferably is no more than 40%. Expressed in another Way, the sugarester concentration in the solution is high-at least 60%. Preferably thesugar ester concentration should be between 70 and 90%. This is becausemost of the sugar esters listed above will not crystallize completelyout of solution or a non-volatile solvent unless the concentration ofdissolved sugar ester is high. Also, if the concentration ofnon-volatile solvent is high (say more than 40%) an excessive amountthereof would be added to the cellulose acetate tow in order to obtainthe desired amount of sugar ester on the tow. This might lead to toomuch bonding of the filaments into a more or less solid rod.

The amount of suger ester as just described Which is applied to thetextile tow to produce a more efiective filter can vary between 5 and50%. In the case of a fine denier (0.6 to 3 denier per filament) filteronly 5-20'% of the sugar ester is required. This is because in such afilter the filaments are closer together, therefore, less tar andnicotine can channel through it Without touching the filaments. In thecase of the filters prepared from the heavier filaments (4-16 denier perfilament) then more protrusions into the spaces between the filamentsmay be desired.

When the cellulose acetate plasticizer type of solvent is used inconjunction with a cellulose acetate textile tow the advantage of usinga one spray operation is realized. Previously on incorporating a solidadditive into a cellulose acetate tow filter by the dusting techniquethe tow was sprayed with the bonding agent and then dusted. By this newmethod of incorporating the solid additive only one operation, sprayingoperation, is required. This is because the sugar ester and the bondingagent are applied from the one solution.

Also, when the cellulose acetate plasticizer type of solvent is used forthe sugar ester, it is desirable to maintain the temperature of thespray solution between 35 and C. This will prevent part of the sugarester from crystallizing out of solution and clogging the spray gun asit is applied to the opened textile tow. Aside from being dissolved in asolvent it is also possible to spray the sugar esters in their meltedstate onto the surface of the textile tow filaments. However, melts ofthe undiluted sugar esters usually have a viscous, tacky characteristicwhich may cause the tow to adhere to the filter rod making equipment.Therefore, the preferred method is to use a small amount of diluent.

The following examples will further illustrate this species of theinvention. In these examples we have limited the sugar derivatives to afew representative examples of the Groups I and II listed above. In thesmoking tests in the examples the same vbrand of kingsize cigarette wasused. It was a brand representing a typical domestic type of cigarettetobacco as already discussed above.

EXAMPLE 5 This example concerns filters prepared from polypropylene towcontaining a sugar ester representing Group I. A continuous crimped (18crimps/in.) tow of polypropylene fibers containing 12,000 filaments of 5denier per filament was pulled over a series of air jets which bloomedit out to a width of 12 inches. While in this spread out condition, itwas sprayed on both sides with a solution consisting of 50 partssorbitol hexa acetate and 50 parts ethyl alcohol. After being sprayed,the tow was pulled back together in the form of a rope or cord and ledthrough a device which paper (cigarette paper) wrapped it into the formof a continuous rod with a circumference equal to that of a standardcigarette. The rod was cut into 15 mm. lengths and these were stored atroom temperature for 48-hours in an open container. During this timeseveral of the 15 mm. filters were opened and observed under themicroscope. After a period of 6 hours, the sugar ester was still visibleon the surface of the filaments in the filters as a liquid. How-ever,after 12 hours, crystals of the sorbitol hexaisobutyrate began to formon the filaments and after 24 hours all of the sugar ester hadcrystallized on the filaments. After 48 hours only a trace amount ofethyl alcohol remained in the filters. Analysis of some of the tipsafter 48 hours showed that they consisted of 79% polypropylene and 21%sorbitol hexa acetate. These values are based on the total weight of thefilter without the paper wrapper. Ten of the tips were placed on'king-size cigarettes which had been shortened by 15 mm. to compensatefor the length of the filter. These cigarettes were smoked to buttlengths of 30 mm. on an automatic smoking machine which produced a 35ml. puff of 2-seconds duration at the rate of one puff per minute. Thesmoke which passed through 9 the filtered cigarettes was collected andanalyzed for its nicotine and tar content.

Filters (15 mm.) were prepared from a continuous and crimped (l8crimps/in.) tow of polypropylene fibers containing 16,000 filaments ofdenier per filament. The method of preparing the filters was identicalto that described above with the exception that no additive was sprayedon the tow. These filters were also attached to 10 of the shortenedking-size cigarettes and the cigarettes were smoked to butt lengths of30 mm. The smoke which passed through these filtered cigarettes wascollected and analyzed for nicotine and tar content.

As a control ten of the unshortened king-size cigarettes were smoked onthe automatic machine to but lengths of 30 mm. The smoke which passedthrough these unfiltered cigarettes was analyzed for nicotine and tarcontent.

Average (10 Mg. tar Mg. nico- Filter mm.) cigarettes) from 10 tine from10 pressure cigarettes cigarettes drop No filter (control) 3.1 170 28Polypropylene tow W out addive 4. O 135 23 Polypropylene tow withsorbitol hcxa acetate crystals 4.1 110 19 EXAMPLE 6 This exampleconcerns filters prepared from viscose tow containing a sugar esterrepresenting Group II. A continuous and crimped (15 crimps/in.) tow ofregenerated cellulose filaments (viscose) containing 12,500 filaments of5 denier per filament was pulled over a series of air jets which bloomedit out to a width o f 12 inches. While on this spread out condition itwas sprayed on both sides with a solution consisting of 60 parts sucroseoctapropionate in 40 parts acetone. After being sprayed the tow waspulled back together and led through a device which paper Wrapped itinto a continuous rod with the circumference the size of a cigarette.The rod was cut into 15 mm. lengths and these were stored at roomtemperature for 48 hours in an open container. Microscopic observationof some of the opened filter tips after this time showed that all of thesucrose octapropionate had crystallized on the filaments in the form ofneedles which protruded out into the spaces between the filaments.Analysis of some of the tips after 48 hours showed that they consistedof 75% regenerated cellulose filaments, 25% sucrose octapropionate and atrace of acetone. These values are based on the total weight of thefilter without the paper wrapper. Ten of these tips were placed onking-size cigarettes which had been shortened by 15 mm. These cigaretteswere smoked to butt lengths of mm. on the automatic smoking machine, Thesmoke which passed through the filtered cigarettes was collected andanalyzed for nicotine and tar content.

Filters (15 mm.) were prepared from a continuous and crimped (15crimps/in.) tow of regenerated cellulose filaments containing 16,350filaments of 5 denier per filament. The method for preparing thesefilters was identical to that described above with the exception that noadditive was sprayed on the tow. These filters were also attached to 10of the shortened king-size cigarettes and the cigarettes were smoked onthe automatic machine 10 to butt lengths of 30 mm. The smoke whichpassed through these filter cigarettes was collected and analyzed fornicotine and tar content.

Average (10 Mg. tar Mg. nico- Filter (15 mm.) cigarettes) from 10 tinefrom 10 pressure cigarettes cigarettes drop Regenerated cellulose towwithout additive 3. 8 138 23 Regenerated cellulose tow with sucroseoctapropionate crystals. 4. O 113 18 EXAMPLE 7 This example concernsfilters prepared from cellulose acetate tow containing a sugar esterrepresenting Group II. A continuous and crimped (l6 crimps per inch) towof cellulose acetate filaments (40% acetyl) containing 15,00 0 filamentsof 2 denier per filament was pulled over a series of air jets whichbloomed it out to a width of 12-inches. While in this spread outcondition, it was sprayed on both sides with a solution consisting ofparts sucrose octaisobutyrate and 25 parts glycerol triacetate. Afterbeing sprayed, the tow was pulled back together and led through a devicewhich paper wrapped it into a continuous rod with the circumference thesize of a cigarette. The rod was cut into 15 mm. lengths and these werestored at room temperature for a total of 5 days. Microscopicobservation of some of the opened filter tips after one day of storagerevealed that only a few crystals of sucrose octaisobutyrate had formedon the filaments. However, after 4 days the surfaces of the filamentswere covered with tiny protrusions of the crystals. Analyses of the tipsshowed that they consisted of 70% cellulose acetate filaments, 22.5%sucrose octaisobutyrate and 7.5% glycerol triacetate. These values arebased on the total weight of the filter without the paper wrapper.

Ten of the rigid tips which had been aged at room temperature for 5 dayswere placed on the king-size cigarettes which had been shortened by 15mm. These cigarettes were smoked to butt lengths of 30' mm. on theautomatic smoking machine and the smoke which passed through the filtercigarettes was collected and analyzed for its nicotine and tar content.

Filters (15 mm.) were prepared from a continuous crimped (1'6crimps/in.) of tow of cellulose acetate (40% acetyl) filamentscontaining 17,500 filaments of 2 denier per filament. The method forpreparing the filters was identical to that described above with theexception that the tow was sprayed with glycerol triacetate alone. Thefinished filters contained cellulose acetate and 10% glycerol triacetatebased on the total weight of the combination without the paper wrapper.After 4 days storage at room temperature, the rigid filters wereattached to 10 of the shortened king-size cigarettes and the cigaretteswere smoked on the automatic smoking machine to butt lengths of 30 mm.The smoke which passed through these filtered cigarettes was collectedand analyzed for nicotine and tar content.

Cellulose acetate tow with glycerol triacetate 4. 2 122 20 Celluloseacetate tow with glycerol triacetate and sucrose octaisobutyrate 4. 3 9515 When compared with the results obtained from the unfilteredcigarettes (Example 5) these values show that the cellulose acetatefilter removed 28% more tar and 29% more nicotine than the tobacco itreplaced. On the same basis, the cellulose acetate containing thesucrose octaisobutyrate crystals removed 44% more tar and 46% morenicotine than the tobacco it replaced. The results also show that addingmore filaments to the filter without the sugar ester did not improve itsfiltering efiiciency to the point where it was equal to the filtercontaining the sugar ester, even though the pressure drops of the twofilters were about equal.

In the above description and examples we have in certain instancesreferred to wrapping the filter rod with a paper wrapper and the paperwrapper which has heretofore been used in the manufacture of tobaccosmoke filters may likewise be used in the present invention. However, ithas been found that certain of the filters of the present invention maybe further improved if they are wrapped in a wrapping paper having1.4-1.7 mils thickness. Or the filter may be wrapped in plastic sheetingsuch as the well-known cellophane sheeting of 0.84.0 mils thickness.

In further detail, when making filters where the filaments have beensprayed with solutions of the sugar ester and plasticizer, a superiorfilter may be produced it the filaments are wrapped with the thickergauge paper or plastic sheeting just mentioned. That is, any tendency ofthe sucrose octaisobutyrate or sucrose octaisobutyrate triacetate orother plasticizer mixture to soften or moisten paper wrapper of lessthan 1.4 mils thickness is obviated by the use of the heavier paper orpaper-plastic sheeting compositions.

In addition, when utilizing polyolefin filaments, or

12 particularly highly crimped filaments, the heavier paper or plasticsheeting has been found to better contain the filaments until internalbonding has taken place and also to provide a firmer, stifier filter.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention as described hereinabove and as defined in the ap pendedclaims.

We claim:

1. A tobacco smoke filter essentially comprised of a bundle made up to asubstantial extent of longitudinally extending synthetic filaments of adenier per filament of less than 16, said filaments carrying on thesurface of the filaments a content of a sugar ester in an amount greaterthan 3% by weight of the filter and a wrapper enclosing the periphery ofthe filter.

2. A filter in accordance with claim 1 wherein the sugar ester is fromthe group consisting of mixed ali- I phatic acid esters of glucose andsucrose.

3. A filter in accordance with claim 1 wherein the filaments also carrya content of plasticizer and a powdered additive.

4. A filter in accordance with claim 1 wherein the filaments arecomprised of crimped continuous longitudinally extending celluloseacetate filaments.

5. A filter in accordance with claim 1 wherein the wrapper is comprisedof paper suitable for wrapping filters and of a thickness greater than1.4 mils.

References Cited in the file of this patent FOREIGN PATENTS 1,051,907Nelson Feb. 4, 1913 2,174,541 Walthausen Oct. 3, 1939 2,215,620Skumburdis Sept. 24, 1940 2,664,374 Slayter et a1. Dec. 29, 19532,694,661 Meyer Nov. 16, 1954 2,763,267 Muller Sept. 18, 1956 2,766,146Ashburn Oct. 9, 1956 2,780,228 Touey Feb. 5, 1957 2,881,770 Touey Apr.14, 1959

1. A TOBACCO SMOKE FILTER ESSENTIALLY COMPRISED OF A BUNDLE MADE UP TO ASUBSTANTIAL EXTENT OF LONGITUDINALLY EXTENDING SYNTHETIC FILAMENTS OF ADENIER PER FILAMENT OF LESS THAN 16, SAID FILAMENTS CARRYING ON THESURFACE OF THE FILAMENTS A CONTENT OF A SUGAR ESTER IN AN AMOUNT